The popularity of electrosurgical techniques and devices has grown dramatically due to their ability to cut, coagulate and vaporize tissue. In one aspect, highly specialized devices for unique, highly-focused applications requiring precise control have been developed and continue to proliferate. In a second aspect, general-purpose electrosurgical systems and devices have been developed which can be produced at low cost and may be used for a wide variety of surgical applications. Over the years, electrosurgical generators frequently referred to as “general-purpose” generators have been developed; by design, these generators are meant to be highly generic and therefore find universal application. Typical of these generators are the IDS-200, IDS-300 and IDS-400 generators by Bovie Medical Corporation (Clearwater, Fla.), the System 5000 and System 2450 generators by Conmed, Incorporated (Utica, N.Y.), the ICC-300, ICC350 and VIO by Erbe (Tubingen, Germany) and the Force FX and Force EZ generators by Valleylab/Covidien, Inc (Colorado Springs, Colo.). These general-purpose generators may have power levels up to 400 Watts when used in monopolar mode, and tend to be equipped with connectors for hand-controlled and foot-controlled operation of such monopolar devices. They are also provided with a separate connector for a monopolar patient return electrode, either a pad or plate style. These general-purpose generators also tend to have a separate bipolar connector for connecting devices such as bipolar coagulating forceps. These bipolar outputs are generally limited to 80 Watts, this power level being sufficient for cautery applications. The connectors of the generators are sometimes also referred to as receptacles, sockets, output connectors or jacks.
The devices designed for use with these general-purpose generators have been largely commoditized. Monopolar devices generally referred to as “electrosurgical pencils” from many manufacturers can be used with generators from many others. Such an electrosurgical pencil is described by Nottke in U.S. Pat. No. 4,427,006. A variety of electrosurgical electrodes may be removably mounted to such devices to accomplish a wide range of medical tasks. The pencils may be either hand- or foot-controlled. Foot-controlled devices tend to include a single-wire electrical power cord that is connected to a “foot pedal” monopolar receptacle on the front panel of a general-purpose generator. Hand-controlled, sometimes referred to as finger-controlled, pencils, tend to use a three-wire power cord that terminates at its proximal end with a linear three-pin connector (also referred to as 3-prong connector or plug), which then connects to the “hand-controlled” monopolar receptacle on the front panel of the generator. The three pin connector of electrosurgical pencils and three pin receptacle on the general-purpose generators have been sufficiently standardized to allow interchangeability between devices and generators produced by many companies, particularly in the U.S.
The interface between the monopolar patient return electrode and the generator has been similarly standardized. The size, configuration and materials of return electrodes and plates vary widely; however, all use a two-wire cord having a standard connector at the proximal end, the connector being configured to fit a mating standardized socket on the front panel of a general-purpose electrosurgical generator.
Devices for use with the generator bipolar output have also been commoditized, the devices being generally bipolar in the classical definition—having two electrodes that are symmetrical in size and shape. Typical of these are various kinds of bipolar coagulating forceps that grasp tissue between their jaws so that current flow is from one jaw to the other so as to desiccate the tissue. The power cords and power connectors for these devices are largely standardized such that the power cords and devices from many manufacturers can be used with generators produced by many other manufacturers. Operation of these bipolar devices is controlled by a foot-pedal. The bipolar generator output is configured for efficient control of bleeding through tissue desiccation while avoiding the sparking which causes tissue destruction. This is accomplished by the generator through limiting the available power, lower voltages, and using a suitable power curve suitable for coagulating tissue held between grasping bipolar jaws like those of bipolar coagulating forceps.
Because the bipolar output of a general-purpose generator is configured to minimize sparking, it is not well suited to use with devices having a return electrode on the device in close proximity to the active electrode and which are specifically designed to cut or vaporize tissue. Using the standard bipolar output of a general-purpose generator to power a device such as a “bipolar” arthroscopy ablator (one with a return electrode in close proximity to the active electrode) would result in extremely inefficient operation at best. Therefore, currently available arthroscopy ablators of this type are used with a dedicated (not general-purpose) generator having specialized output power characteristics and/or modulated waveforms. Examples of such dedicated bipolar radiofrequency generators for arthroscopy include the System 2000, Atlas and Coblator II by Arthrocare (Austin Tex.), SERFAS by Stryker (San Jose, Calif.), and VAPR by DePuy Mitek Inc (Raynham, Mass.). Dedicated bipolar generators are also available for other medical procedures.
Although general-purpose electrosurgical generators are available in every operating room, it is necessary to use a special purpose generator for return-in-close-proximity applications that primarily cut or vaporize tissue. Because the efficiency of cutting or vaporizing tissue with such a device when powered by the bipolar receptacle of a general-purpose generator is unacceptably low, there are not low-cost commoditized devices having a return electrode in close proximity on the device available for use with these general-purpose generators.
However, specialized dedicated equipment is not preferred in a hospital setting. Not only does the procurement and storage contribute to overhead costs, but, given that such specialized equipment tend to be less ubiquitous, additional transport and/or scheduling is often necessitated. To address this problem, attempts have been made to connect bipolar devices to the monopolar outputs of standard multipurpose electrosurgical generators. However, as discussed in detail below, all require either reconfiguration of or modification to the output signal (e.g., load curve, ablation curve, etc.) or the use of additional electrical components such as resistors, capacitors, inductors, transformers and/or other interface circuitry.
In U.S. Pat. No. 5,633,578, Eggers et al. teach the connection of haemostatic bipolar devices to the monopolar outputs of a standard multipurpose generator using conversion devices. The intent is to provide “adaptors for use with conventional electrosurgical generators to provide voltage output waveforms effective in reducing coagulum buildup, and to alleviate sticking, on hemostatic electrosurgical instruments”. This is accomplished by the use of external, voltage-limiting circuitry for modifying the generator output waveforms in order to prevent arcing. However, the systems taught are not applicable to devices used for cutting and bulk vaporization since these require sparking, and decreasing the voltage decreases the efficiency of these devices to generate sparks.
In U.S. Patent Application Publication No. 2007/0016182, Lipson et al. teach the connection of fluid-assisted bipolar devices to the monopolar outputs of a general-purpose generator using an adaptor that modifies the power levels and load curves of the generator. Quoting Lipson, “[i]n order to reduce monopolar voltage and impedance ranges to desirable levels for bipolar use, a transformer may be placed in series circuit configuration between the electrodes of bipolar device 5i and the monopolar mode power output of the generator 6.” The intent is to use circuitry distal to the generator to inhibit sparking caused by the high voltages present in monopolar outputs. Accordingly, the resulting RF power has inefficient characteristics for tissue vaporization. Again in U.S. Pat. No. 7,909,820 Lipson et al. teach the use of a transformer distal to the generator in order to change its characteristics,
In U.S. Patent Application Publication No. 2004/0030330, Brassell et al. teach a bipolar device for rasping tissue while applying RF energy thereto, together with an adaptor with circuitry for connecting the device to the monopolar outputs of a general-purpose electrosurgical generator. Quoting Brassell, “[g]enerally, generator 32 provides constant electric power to adapter module 34, which converts the power to a form useable by probe 36, e.g., approximately constant voltage.” and “Advantages of the invention may include . . . (v) minimizing the possibility of runaway current during electrosurgery by providing an adapter that converts constant power output from a generator to constant voltage output for an electrosurgical probe”. Apparently this was a unique requirement for the disclosed bipolar device. To achieve these goals Brassell teach circuitry distal to the generator adapted to convert substantially constant power to constant voltage output.
In U.S. Pat. Application Publication No. 2012/0095457, Morgan et al. disclose a method for connecting a non-vaporizing bipolar device to the monopolar output on a standard generator through the use of “active components” connected between the output and return cabling of the generator, distal to the generator. The active components are used to match the impedance of the load to that of the generator. This matching allows the use of bipolar devices at low power levels. However, this performance is achieved by eliminating one of the wires connected to the standard three-pin hand-control monopolar output of the generator so that the bipolar device can operate only in one mode, either Cut only or Coag only. Thus, the operator is able to activate the device in the chosen waveform and power level, but does not have the ability to switch between waveforms and preset power levels for Cut and Coag functions. This can seriously limit the surgeon ability to deliver the optimal therapeutic effect to the patient. Furthermore, this approach requires adding external, non-standard bridging/balancing electrical components between the generator and the electrosurgical device in order to substantially mimic the load response produced by an external return circuit of a monopolar electrosurgical unit. Similarly, in U.S. Patent Application Publication No. 2010/0324550, Morgan et al. teach the use of a current bridge, distal to the generator, in order to change the generator characteristics by producing a matched impedance to a load condition. Morgan teaches away from vaporization.
While these various adaptors and adapting methods are suitable and necessary for their associated devices, their effect is to produce outputs with characteristics that are less suited to the vaporization of tissue than those of the standard un-modified monopolar output. Additionally, they add unnecessary complexity and cost if the outputs are to be used primarily for tissue vaporization and cutting. Adding external components and circuitry distal to the generator other than wires, and connecting or interconnecting components is outside the scope of this invention. The present invention herein disclosed addresses these and other problems by providing a novel cable assembly that is free from additional interface circuitry or electronic components, such as resistors, capacitors, inductors, and transformers, and suitable for connecting a bipolar device to the monopolar active and return receptacles of a standard multipurpose electrosurgical generator.